Maya astronomy is the study of the Moon, planets, Milky Way, Sun, and astronomical phenomena by the Precolumbian Maya civilization of Mesoamerica. The Classic Maya in particular developed some of the most accurate pre-telescope astronomy in the world, aided by their fully developed writing system and their positional numeral system, both of which are fully indigenous to Mesoamerica. The Classic Maya understood many astronomical phenomena: for example, their estimate of the length of the synodic month was more accurate than Ptolemy's, and their calculation of the length of the tropical solar year was more accurate than that of the Spanish when the latter first arrived. One of the purposes that Maya priest-astronomers observed the celestial movement is to discover the pattern that supports the agricultural schedule.Milbrath, S. (2017). MAYA ASTRONOMICAL OBSERVATIONS AND THE AGRICULTURAL CYCLE IN THE POSTCLASSIC MADRID CODEX. Ancient Mesoamerica, 28(2), 489–505. doi:10.1017/S0956536117000189 Many temples from the Maya architecture have features oriented to celestial events.
European and Maya calendars
European calendar
In 46 BC Julius Caesar decreed that the year would be made up of twelve months of approximately 30 days each to make a year of 365 days and a leap year of 366 days. The civil year had 365.25 days. This is the Julian calendar. The solar year has 365.2422 days and by 1582 there was an appreciable discrepancy between the winter solstice and Christmas and the vernal equinox and Easter. Pope Gregory XIII, with the help of Italian astronomer Aloysius Lilius (Luigi Lilio), reformed this system by abolishing the days October 5 through October 14, 1582. This brought the civil and tropical years back into line. He also missed three days every four centuries by decreeing that centuries are only leap years if they are evenly divisible by 400. So for example 1700, 1800, and 1900 are not leap years but 1600 and 2000 are. This is the Gregorian calendar. Astronomers use the Julian/Gregorian calendar. Dates before 46 BC are converted to the Julian calendar. This is the proleptic Julian calendar. Astronomical calculations return a year zero and years before that are negative numbers. This is astronomical dating. There is no year zero in historical dating. In historical dating the year 1 BC is followed by the year 1 so for example, the year −3113 (astronomical dating) is the same as 3114 BC (historical dating).Meeus 2009 pp. 59–64
Many mayanists convert Maya calendar dates into the proleptic Gregorian calendar. In this calendar, Julian calendar dates are revised as if the Gregorian calendar had been in use before October 15, 1582. These dates must be converted to astronomical dates before they can be used to study Maya astronomy because astronomers use the Julian/Gregorian calendar. Proleptic Gregorian dates vary substantially from astronomical dates. For example, the mythical creation date in the Maya calendar is August 11, 3114 BC in the proleptic Gregorian calendar and September 6, −3113 astronomical.
Julian days
Astronomers describe time as a number of days and a fraction of a day since noon January 1, −4712 Greenwich Mean Time. The Julian day starts at noon because they are interested in things that are visible at night. The number of days and fraction of a day elapsed since this time is a Julian day. The whole number of days elapsed since this time is a Julian day number.
Maya calendars
There are three main Maya calendars:
The Long Count is a count of days. The Long Count calendar was particularly notable for its accuracy in tracking celestial events. For example, the Maya were able to predict solar eclipses and the movements of Venus with remarkable precision. This knowledge was not only used for agricultural planning but also played a significant role in religious ceremonies and royal legitimization. There are examples of Long Counts with many places but most of them give five places since the mythical creation date – 13.0.0.0.0.
There were several types of calendars to count the days in Maya, letting the Maya associate the different calendars. Both agricultural cycles of the Tzotzil in southern Mexico and the Chorti of Guatemala starts 260 days from early February.Milbrath, S. (2017). MAYA ASTRONOMICAL OBSERVATIONS AND THE AGRICULTURAL CYCLE IN THE POSTCLASSIC MADRID CODEX. Ancient Mesoamerica, 28(2), p.497 doi:10.1017/S0956536117000189 The beginning of the Chorti seasonal calendar has flexibility to be the first visible moon around February 8th, which is a day or two later than the astronomical new moon.Milbrath, S. (2017). MAYA ASTRONOMICAL OBSERVATIONS AND THE AGRICULTURAL CYCLE IN THE POSTCLASSIC MADRID CODEX. Ancient Mesoamerica, 28(2), p.497 doi:10.1017/S0956536117000189 Tzotzil people integrated the Chorti 260-day with a solid 365-day calendar.Milbrath, S. (2017). MAYA ASTRONOMICAL OBSERVATIONS AND THE AGRICULTURAL CYCLE IN THE POSTCLASSIC MADRID CODEX. Ancient Mesoamerica, 28(2), p.497 doi:10.1017/S0956536117000189 Below explains the structure of each type of calendar.
The Tzolkʼin is a 260-day calendar made up of a day from one to 13 and 20 day names. By pairing the numbers with the 20 names, that leaves 260 unique days with every combination of numbers/names happening once. The 260-day calendar led the Maya people to observe the lunar phenomena to know the agricultural cycle, even today.Milbrath, S. (2017). MAYA ASTRONOMICAL OBSERVATIONS AND THE AGRICULTURAL CYCLE IN THE POSTCLASSIC MADRID CODEX. Ancient Mesoamerica, 28(2), pp.499 and 503 doi:10.1017/S0956536117000189 Especially, a solar eclipse during the agricultural season was carefully observed, since it is the pinpoint of the new lunar occurrence.Milbrath, S. (2017). MAYA ASTRONOMICAL OBSERVATIONS AND THE AGRICULTURAL CYCLE IN THE POSTCLASSIC MADRID CODEX. Ancient Mesoamerica, 28(2), pp.499 and 505 doi:10.1017/S0956536117000189 Also, this calendar was of the most sacred to the Maya, and was used as an almanac to determine farming cycles, and for religious practices to specify dates for ceremonies. These 260 days were each considered individual gods and goddesses that were not persuaded by a higher power. Unlike the 365 day year, this 260 day year was used less for counting/calculations, and more to arrange tasks, celebrations, ceremonies, etc. In some present day Maya communities, this 260 day almanac is still used, mostly for religious practices.
The Haab' is a 365-day year made up of a day of zero to 19 and 18 months with five unlucky days at the end of the year.
When the Tzolkʼin and Haabʼ are both given, the date is called a calendar round. The same calendar round repeats every 18,980 days – approximately 52 years. The calendar round on the mythical starting date of this creation was 4 Ahau 8 Kumk'u. When this date occurs again it is called a calendar round completion.
A Year Bearer is a Tzolkʼin day name that occurs on the first day of the Haab'. A number of different year bearer systems were in use in Mesoamerica.Edmonson 1988
Correlating the Maya and European calendar
The Maya and European calendars are correlated by using the Julian day number of the starting date of the current creation — 13.0.0.0.0, 4 Ajaw, 8 Kumk'u. The Julian day number of noon on this day was 584,283. This is the GMT correlation.
Sources of astronomical inscriptions
Maya codices
At the time of the Spanish conquest the Maya had many books. These were painted on folding bark cloth. The Spanish conquistadors and Catholic priests destroyed them whenever they found them. The most infamous example of this was the burning of a large number of these in Maní, Yucatán by Bishop Diego de Landa in July 1562. Only four of these codices exist today. These are the Dresden, Madrid, Paris and Grolier codices. The Dresden Codex is an astronomical Almanac. Although they, using the codex, did not successfully make a prediction of an eclipse in their place, eclipse tables in the Dresden Codex provided Maya people with opportunities to predict when an eclipse would occur in someplace.Milbrath, S. (2017). MAYA ASTRONOMICAL OBSERVATIONS AND THE AGRICULTURAL CYCLE IN THE POSTCLASSIC MADRID CODEX. Ancient Mesoamerica, 28(2), 489–505. doi:10.1017/S0956536117000189 The Madrid Codex mainly consists of almanacs and horoscopes that were used to help Maya priests in the performance of their ceremonies and divinatory rituals. It also contains astronomical tables, although less than are found in the other three surviving Maya codices. The Paris Codex contains prophecies for tuns and katuns (see Mesoamerican Long Count calendar), and a Maya zodiac. The Grolier Codex is a Venus almanac.
Ernst Förstemann, a librarian at the Royal Public Library of Dresden, recognized that the Dresden Codex is an astronomical almanac and was able to decipher much of it in the early 20th century.Forstemann 1906
Maya monuments
Maya stelae
The Maya erected a large number of stelae. These had a Long Count date. They also included a supplementary series. The supplementary series included lunar data – the number of days elapsed in the current lunation, the length of the lunation and the number of the lunation in a series of six. Some of them included an 819-day count which may be a count of the days in a cycle associated with Jupiter. See Jupiter and Saturn below. Some other astronomical events were recorded, for example the eclipse warning on Quirigua Stela E – 9.17.0.0.0. A partial solar eclipse was visible in Mesoamerica two days later on 9.17.0.0.2 – Friday January 18, 771.
Santa Elena Poco Uinic Stela 3 has a date of 9.17.19.13.16 5 K'ib' 14 Ch'en, July 16, 790, with a solar eclipse glyph. A total solar eclipse crossed directly over the site three days later on July 16, 790.
Calendric inscriptions Many Mayan temples were inscribed with hieroglyphic texts. These contain both calendric and astronomical content.
An archaeoastronomical study by Martínez-González examined the chronological correspondence between the enthronement of Ukit Kan Le'k Tok', dated to 26 May 770 in the Mural of the 96 Glyphs at Ekʼ Balam, and Chinese records of comet C/770 K1 from the same day. The reconstructed orbit placed the comet in the northeastern sky before sunrise, under conditions compatible with naked-eye visibility from northern Yucatán.
Methods of astronomical observation
Maya astronomy was naked-eye astronomy based on the observations of the azimuths of the rising and setting of heavenly bodies.Aveni 2001 Chapter III pp. 49–95 City planning and alignment was often arranged in line with astronomical paths and events.Aveni 2001, Chapter V pp. 217–321 The Maya also believed that the will and actions of gods could be interpreted in the alignment of the planets and stars.
Many wells located in Mayan ruins were also observatories of the zenithal passage of the sun.
One of the most studied sites for the topic of Mayan astronomy is the El Caracol at Chichen Itza. The Caracol is an observatory aligned to follow the path of Venus through the year.Aveni 2001 pp. 3, 92, 2024, 206, 272, 273, 273–282, 275, 280, 287–288, 361n.33 The grand staircase leading to the once cylindrical structure deviates 27.5 degrees from the alignment of the surrounding buildings to align with the northern extreme of Venus; the northeast-southwest diagonal of the site aligns with the sunrise of the summer solstice and the sunset of the winter solstice.
Astronomical observations
Solar